Design of Tributary Estuary Wetland in Liaohe Conservation Area

In the past decades, the natural wetlands in the Liaohe Conservation Area were destroyed due to severe branch river pollution and ecological water shortages. Considering the various influencing factors, such as water conservancy engineering, ecological restoration and biological diversity conservation, nine polluted branches were identified. A wetland system composed mainly of oxbow-lake wetland and pit-wetland were designed. Through this planning, a healthy river ecosystem including good water quality, healthy ecology and beautiful landscape can be restored. The area of estuary wetlands was calculated by the tributary pollution load and water quantity of dry season. Water hydraulic load was generally designed as 0.01-0.1 m³/(m²?d) and 0.1-1.5 m³/(m²?d) in dry season and wet season, respectively. The hydraulic retention time was designed as 5 to 7 days in normal time and 1 day in flood period. The design effluent of COD_Cr and ammonia nitrogen could be decreased to less than 50 mg/L and 5 mg/L respectively after passing through the estuary wetlands. The construction of Liaohe river estuary wetlands offered the opportunity for water quality improvement in Liaohe river branch.